Transmissivity (T) and Hydraulic apertures are often calculated from hydraulic test data obtained in fractured rock using analytical solutions such as the Thiem and cubic law equations developed for flow through unconsolidated porous media. These analytical solutions use a variety of simplifying assumptions, which are often violated due to the complex nature of flow through fractured rock systems which introduces error into the calculated hydraulic apertures. A 3-D discrete fracture network numerical model (SMOKER) for flow in dual-permeability media was used to simulate constant-head straddle packer tests to assess the errors in fracture characterization that result from deviations from the Thiem and cubic law assumptions caused by permeable rock matrix, variable aperture fractures, and complex flow patterns. The simulations indicate that SMOKER offers potential as a useful tool for representing non-ideal scenarios of rock and fracture network characteristics to assist in estimates and error analysis in T values and resultant errors in hydraulic aperture.